How do I determine measurement uncertainty for a CMM in accordance with ISO 10360?

We have a bridge CMM that passed its ISO 10360-2 acceptance test (MPEe stated by the manufacturer). For our ISO/IEC 17025 scope I need a task-specific measurement uncertainty, not just the MPE. What is the accepted route from the 10360 test result to an uncertainty I can report on certificates?

2 Answers

Metrology Atlas Editorial ✓ Verified expert answer 1 day ago

The ISO 10360 result alone is not a measurement uncertainty — it verifies the machine meets its specification. For task-specific uncertainty the recognized routes are:

ISO 15530-3 (substitution): measure a calibrated workpiece similar to your production part in the same way you measure production parts. The uncertainty combines the calibration uncertainty of the reference part, the observed process variation, and systematic differences. This is the most practical accredited route.
Uncertainty budget (GUM): build a model from MPEe, probing dispersion (10360-5), thermal effects (part and scale CTE × temperature deviation from 20 °C), fixturing and strategy effects. Defensible for simple length-like tasks.
Simulation (ISO/TS 15530-4): virtual CMM software if you have it.

Accreditation assessors generally expect 15530-3 evidence or a documented budget per task family, plus interim checks with a check standard between reverifications.

Metrology Atlas Editorial 1 day ago

One practical warning: don't forget the temperature term. On a 500 mm steel part, a 2 °C departure from 20 °C is ~11.5 µm of expansion (steel ≈ 11.5 µm/m·°C). On many shop-floor CMMs that term alone dwarfs the MPEe.

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